Take a femur for example. Most everyone knows that long skeletal bones are hollow, with sp

Take a femur for example.  Most everyone knows that long skeletal bones are 
hollow, with spongy ends and hard shafts.  The hard shaft is not simply
solid material, like concrete; it's composed of many (hundreds?  thousands?)
tiny cylinders called osteons.  The osteons have several layers; each is
composed of a slanted spiral of collagen fibers (elastic) with the spaces
filled up by minerals (the hard, brittle part).  In adjacent layers, the
slanted collagen spirals are oriented _in diffent directions_, so that 
each osteon is very resistant to stress coming from a single direction.
The hard shaft is made up of osteons stuck together with more minerals
and connective tissue (like the collagen, but not as elastic).  The 
construction is remarkably like a fiberglass/resin or graphite/resin
composite, but each of the fibers is microstructured to be flexible, yet
stress resistant!  The hard part of the bone (shaft) is a tube of this
stuff.  The ends are thin shells of this, but full of spongy bone.

The inner, spongy part has many stuctures in it called trabeculae.  These are
similar to (and derived from) osteons, and perform a "guy wire" function.
They are located along tension stress lines in the bone (no fooling- I
saw a diagram of predicted stress lines next to an actual femur cross section-
remarkable correlation).  The trabeculae act like cables to, e.g., keep the
head of the femur from breaking off.  (It's at an angle at the top of the
shaft, you know.)

So, a bone is composed of a hard, elastic shell which is itself composed of
myriad tiny cylinders all built in such a way as to resist stress from 
all directions simultaneously.  If that weren't enough, guy wires inside
the hollow center transfer tension stress to the strong shaft.  A 
remarkable piece of engineering!  Almost makes one believe in divine
guidance!